Solid-state dye-sensitized solar cells have been the focus of much attention over the past few years. We have recently been able to demonstrate efficiencies in excess of 4% and further improvements are expected. Here we compare a range of different hole conductor materials and investigate a number of key parameters which affect their performance. Wetting and pore-filling of the nanoporous TiO2 layer by the hole transporter appears to play a critical role in determining the final efficiency of the cell. A comparison of our results shows the importance of complete filling in contrast to just wetting of the nanoporous TiO2 layer, which is generally underestimated. (c) 2005 Elsevier B.V. All rights reserved.